The impact of a tDCS and cognitive training intervention on task-based functional connectivity

Abstract

Declines in several cognitive domains, most notably processing speed, occur in non-pathological aging. Given the exponential growth of the older adult population, declines in cognition serve as a significant public health issue that must be addressed. Promising studies have shown that cognitive training in older adults, particularly using the useful field of view (UFOV) paradigm, can improve cognition with moderate to large effect sizes. Additionally, meta-analyses have found that transcranial direct current stimulation (tDCS), a non-invasive form of brain stimulation, can improve cognition in attention/processing speed and working memory. However, only a handful of studies have looked at concomitant tDCS and cognitive training, usually with short interventions and small sample sizes. The current study assessed the effect of a tDCS (active versus sham) and a 3-month cognitive training intervention on task-based functional connectivity during completion of the UFOV task in a large older adult sample (N = 153). We found significant increased functional connectivity between the left and right pars triangularis (the ROIs closest to the electrodes) following active, but not sham tDCS. Additionally, we see trending behavioral improvements associated with these functional connectivity changes in the active tDCS group, but not sham. Collectively, these findings suggest that tDCS and cognitive training can be an effective modulator of task-based functional connectivity above and beyond a cognitive training intervention alone.

Keywords: Cognitive training; Functional connectivity; Transcranial direct current stimulation; UFOV; tDCS.

Fig. 1

Useful field of view (UFOV) fMRI task. Adapted from Woods et al

Fig. 2

UFOV network and nodes displayed on grey matter mask, depicting anterior, superior, and lateral right hemisphere views, respectively. Adapted from Kraft et al

Fig. 3

Connectome ring of ROI-to-ROI task-based functional connectivity using the 10 a priori spherical ROIs. The color of the connections and color bar refer to connectivity t-values

Fig. 4

Raincloud plots depicting the significant tDCS group by timepoint interaction on within-network connectivity of the UFOV network, controlling for age, sex, years of education, scanner type, and UFOV accuracy change score (standardized predicted values)

Fig. 5

Scatterplot depicting the relationship between average within-network connectivity of the UFOV network and accuracy on the UFOV fMRI task, controlling for age, sex, years of education, and scanner type (standardized predicted values). Shaded region represents the 95% confidence interval of the regression line

Fig. 6

Electric field distribution model of the F3 (cathode) and F4 (anode) montage used in the current study